20+7 = 30-20 = 90+9= 60-30 = 24+6 =
51+8= 7+83= 85-5 = 90-70= 45+20=
96-7 = 65+20= 39+8= 4+65=
18+50-7= 80-60+35= 90-(60+30)= 63-(76-70)=